The field of the invention relates generally to micro-fabrication of structures. More particularly, the present invention is directed to creating recessed structures utilizing a trim etch process followed by reverse toning of the recessed structures.
Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication have been employed include biotechnology, optical technology, mechanical systems and the like.
A method of reducing the minimum feature dimension of structures formed from micro-fabrication is disclosed in U.S. Pat. No. 6,541,360 to Plat et al. Plat et al. describes a bi-layer trim etch process to form integrated circuit gate structures having small critical dimensions. More specifically, Plat et al. describes forming a multi-layered structure by depositing an organic underlayer over a layer of polysilicon, depositing an imaging layer over the organic underlayer, and patterning the imaging layer. The imaging layer is then utilized as a hard mask to selectively trim etch the organic underlayer to form a pattern smaller than that produced by the imaging layer. The hard mask imaging layer is then removed, and finally, the portions of the polysilicon layer are etched using the pattern formed by the organic underlayer. This allows for formation of a gate pattern with widths less than the widths of the pattern of the imaging layer.
What is desired, however, is a technique to form a structure having holes/trenches of a reduced critical dimension.